No, it's not.
Flat iron steaks come from the shoulder of the cow, and were previously avoided, because there's a tough piece of gristle running right through the middle of the cut. Modern butchery removes this, which is why you'll sometimes see a cut running along the middle of the steak.
If you like your steak well-done you should avoid flat iron - it will be tough. Cook it medium rare, or (my preference) rare and you'll find it tender and absolutely delicious. I think it beats fillet any day - we barbecue it in the summer, and cut it into half inch strips when it's done. Some salt and pepper, a crispy-skinned jacket potato, some nice fresh salad, a glass or two of your favourite beverage, and you can feast like a king.
I first encountered it at a barbecue in Australia, where it's referred to as Top Blade.
Enjoy your steak.